Voltage regulator circuit



May 22,1945.-

R. V. LITTLE, JR

VOLTAGE REGULATOR CIRCUIT Filed June 18, 1943 mailin cam Enventor(Ittorneg Patented May 22, 1945 VOLTAGE REGULATOR CIRCUIT Ralph V.Little, Jr., Swar'thmore, Pa., assignor to Radio Corporation of America,a. corporation of Delaware Application June 18, 1943, Serial No. 491,420

6 Claims. (OI. 171-312) This invention pertains generally to regulatedpower supply circuits and more particularly to a voltage regulator for asource of rectified and filtered alternating potential wherein theregulator provides a power source having substantially constant outputvoltage and a low output impedance.

Various types of voltage regulators have been used. heretofore inconjunction with conventional power supply circuits for thermionic tubeapparatus. Besides regulating the output voltage of a power supplywithin predetermined small limits, one of the prime-requisites of avoltage regulator is to provide a power source having extremely lowoutput impedance in order that variations in load or source impedancesmay haveminimum effect upon'the regulated output voltage.

The instant invention is an improvement over the invention described inthe copending U. S. application of W. J. Poch, Ser. No. 515,038, filedDecember 20,1943, and assigned to the same assignee as the instantapplication. It contemplates the use of a thermionic regulator tubehaving an anode. a cathode and at least one control-electrode whereinthe anode-cathode circuit of the tube provides a shunt impedance pathacross the output of a filter which is connected to the output of aconventional high voltage rectifier. A voltage divider, comprising apair of serially-connected resistors, one of which is shunted by acapacitor, is also connected across the output of the filtered powersupply. The anode of a first thermionic tube amplifier is connecteddirectly to the positive output terminal of the filtered power supply.The anode of a second triode amplifier tube is also connected to thepositive terminal of the filtered power supply through an anode couplinresistor. The cathodes of the two amplifier tubes are connected togetherand are connected, through a common cathode resistor, to the negativeterminal of the filtered power supply. .The anode of the secondamplifier tube is connected through, for example, a one microfaradcapacitor to the control electrode of the thermionic regulator tube.

Briefly, the operation of the system is as follows: The regulator tubeprovides a shunt impedance path across the output of the filtered powersupply. A portion of the regulated output voltage degenerativelycontrols the first amplifier tube which is cathode coupled to thesecondamplifier tube. Suitable phase reversal is provided thereby for applyingregulating voltages to the control electrode of the thermionic regulatortube, thereby varying the impedance of the regulator tube and the shuntimpedance path across the filtered power supply.

It will be seen that the circuit will compensate readily forsubstantially all except very gradual line surges, for residual hum andfor fluctuations caused by all except very gradual variations in sourceand load impedances. Since the output voltage will remain substantiallyconstant, notwithstanding variations in applied voltage and in loadimpedances, the effective output impedance of the circuit will beextremely low. The use of large capacitors across the output of theregulated voltage source therefore becomes unnecessary, resulting inconsiderable economy in space and cost.

Among the objects of the invention are to pro vide an improved voltageregulator for a source of uni-directional voltage. A further object isto provide an improved'voltage regulator having a relatively smallstatic current drain. Another objector the invention is to provide animproved voltage regulator for a uni-directional voltage.

source wherein a portion of the output regulated voltage isdegeneratively applied to anamplifier which is connected to vary theshunt impedance of a regulator tube connected across the uni-directionalvoltage source. A further object of the invention is to provide animproved regulator circuit for controlling the output voltage of afiltered power supply circuit wherein a portion of the regulated outputvoltage is degeneratively applied to a first amplifier tube, and theoutput of the first amplifier tube is cathode-coupled to a secondamplifier tube to provide control potentials which are applied to thecontrol electrode of athermionic regulator tube connected across theoutput of the filtered power supply. Another obprovide an improvedvoltage regulator for a which the single figure. thereof is a schematiccircuit diagram of a preferred embodiment.

Referring to the drawing. the circuit includes a conventional filteredhigh voltage power supnected to the. control electrode ply whichcomprises a power transformer I having a primary winding 2 connected toa source of alternating potential. The terminals 01' the high voltagesecondary winding 3 are connected to the anodes of a full wave rectifiertube 4. A cathode of the full wave rectifier tube 4 is connected to alow voltage secondary winding 5 of the transformer I. The cathode of therectifier tube 4 is also connected to the positive output terminal 6.The center tap of the high voltage secondary winding of the transformeri is connected, through a relatively high reactance coil 1, to thegrounded negative output terminal 6'. A first filter capacitor 8 isconnected between the cathode of the rectifier tube 4 and the center tapof the high voltage secondary winding 3 of the transformer l. A secondfilter condenser 9 is connected from the cathode of the rectifier tube 4to the grounded output terminal of the reactance coil I.

The anode of a thermionic regulator tub'e I0 is connected to the cathodeof the rectifier tube 4. The anode is also connected through a screencoupling resistor H to the screen electrode of the regulator tube l0.-The cathode of the regulator tube [0 is connected to the groundedterminal of the filtered power supply circuit. Suit able negative biaspotential for the control electrode of the thermionic regulator tube I0i applied thereto through the series resistors l2, l3, I4, which areconnected to the center tap of the high voltage secondary winding 3 ofthe transformer l. Additional filtering of this bias potential isprovided by third and fourth filter capacitors I5, l6, connectedrespectively between the junctions of the series resistors l2, I3, andI4 and the grounded terminal of the power supply circuit.

The anode of a first amplifier tube I1 is connected to the positiveoutput terminal 6 and to the cathode of the rectifier tube 4. The. anodeof a second amplifier tube It! is connected, throughyan anode couplingresistor I 9, to the cathode of the rectifier tube 4.

tively, are connected together, and are connected, through a commoncathode resistor 20, to the grounded negative terminal 6 of the powersupply. A voltage divider, comprising a pair of serially connectedresistors 2|, 22, is connected between the output terminals 6 and 6'. Acapacitor 23 is connected across the first series resistor 2|. Thejunction of the series resistors 2|, 22 is conof the first amplifiertube l1.

It will be seen that variations in the output voltage applied to theoutput terminal 8, 6' will be applied degeneratlvely to drive the firstamregulated output voltage is coupled degeneratively to a controlelectrode of a thermionic regulator tube comprising a shunt impedancepath across the output of the source oi. uni-directionalpotential. Theresultant circuit provides substantially constant output potential at aneffectively low power supply output impedance.

I claim as my invention:

1. A voltage regulator for a source of direct voltage including athermionic regulator tube having a cathode, an anode and at least onecontrol electrode, means connecting the anodecathode circuit of saidtube across said voltage source, a pair of thermionic amplifier tubeshaving a common cathode circuit, means connecting the anode-cathodecircuits of said amplifier tubes across said voltage source, meansincluding said source for degeneratively controlling one of saidamplifier tubes, capacitive means coupling said one amplifier tube tothe other of said amplifier tubes, and means coupling said other of saidamplifier tubes to a control electrode of said regulator tube forvarying the shunt impedance of said regulator tube across said voltagesource.

2. A voltage regulator for a source of uni-directional voltage includinga thermionic regulator tube having a cathode,.an anode and at least onecontrol electrode, means including said tube The cathodes of the firstand second amplifier tubes ll, I8 respectube l8 which are appliedthrough a coupling which is connected across the output of the filteredpower supply.

Thus the-invention disclosed comprises an improved voltage regulatorcircuit for a source 01' uni-directional potential wherein a portion ofthe providing a shunt impedance path across said source, a pair ofcascaded amplifier tubes each having a cathode, an anode, at least onecontrol electrode and a common cathode resistor, means fordegeneratively applying at least a portion of said voltage to saidcontrol electrode of the first of said cascaded amplifier tubes,capacitive means coupling said anode of said first amplifier tube to acontrol electrode of the second of said amplifier tubes, means forderiving a control potential from said second of said amplifier tubes,and means for applying said control potential to said regulator tube tovary said shunt impedance in response to variations in saidunidirectional voltage.

3. A voltage regulator for a source of direct voltage 'including athermionic regulator tube having a cathode, an anode and at least onecontrol electrode, means including said tube providing a shunt impedancepath across said voltage source. a pair of cascaded thermionic amplifiertubes having a common cathode circuit, means connecting said amplifiertubes across said source, means for degeneratively applying at least apor tion of said voltage to one of said amplifier tubes, capacitivemeans coupling said one amplifier tube to the other of said amplifiertubes, means for deriving a control potential from said other of saidamplifier tubes, and means for applying said control potential to saidregulator tube to vary said shunt impedance in response to variations insaid direct voltage. l

4. A'voltage regulator for a source of unidirectional voltage includinga thermionic regulator tube having a cathode, an anode and at least onecontrol electrode, means including said tube providing a shunt impedancepath across said source, a pair of cascaded amplifier tubes each havinga cathode, an anode, at least one control electrode and a common cathoderesistor, means for degeneratively applying at least a portion of saidvoltage to said control electrode of the first of said cascadedamplifier tubes, capacitive means coupling said anode of said firstamplifier tube to a control electrode of ,the second of said ampliflertubes, means for deriving a control potential from said second of saidamplifier tubes, and

means for applying said control potential to said control electrode ofsaid regulator tube to vary said shunt impedance in response tovariations in said unidirectional voltage.

5. A voltage regulator for a source of unidirectional voltage includinga thermionic regulator tube having a, cathode, an anode and at least onecontrol electrode, means including said tube providing a shunt impedancepath across said source, a pair of cascaded amplifier tubes each havinga cathode, an anode, at least one control electrode and a common cathoderesistor, means including a capacitor and a resistive network iordegeneratively applying at least a portion or said voltage to saidcontrol electrode of the first of said cascaded amplifier tubes,capacitive means coupling said anode of said first amplifier tube to acontrol electrode of the second of said amplifier tubes, means forderiving a control potential irom said second of said amplifier tubes,and means for applying said control potential to said control electrodeor said regulator tube to vary said shunt. impedance in response tovariations in said unidirectional voltase.

6. A voltage regulator for a source of unidirectional voltage includinga thermionic regulator tube having a cathode, an anode and at least onecontrol electrode, means including said tube providing a shunt impedancepath across said source, a pair of cascaded amplifier tubes each havinga cathode, an anode, at least one control electrode and a common cathoderesistor. means including a capacitor and a resistive network fordegeneratively applying at least a por- RALPH V. m, JI.

